Veneer defect cutting machine



Jan. 30, 1951 E. H. JACOBSON VENEER DEFECT CUTTING MACHINE Filed March51, 1945 2 Sheets-Sheet 2 Patented jan. 30,

N'ITED STATES PATENT ()FFICE 2,539,742 w I V VENEER DEFECT mime meansElmer H, Jacobson, Lebanojm breg-g,aesigner i6 CascadesjPlywoodCorporation, Portland, Oregi, a corporationofDelaware ApplicationMarch-31, 1945, Serial No; b85949 Claims. (c1. ire-2) It is verydesirable that the surface plies of plywood be free'of defects, such asknots and pitch pockets. Plywood is made ordinarily in rather tice inthe coniferous plywood industry to cut out defective areas from veneersheets which are to be used as surface pliesof pywood, and to insertpatches in the apertures thus formed prior to fabrication of theplywood. V

Machines have been developed for removing the defective areas, and othermachines are available for inserting patches. The Gragg Patent No.2,071,519, issued February 23, 1937, for example, shows a machine ofthis general type. The present invention relates to improvements inmachines for cutting holes in veneer to eliminate knots, pitch pocketsand the like. p r

Defect cutting machines form an aperture in a veneer sheet of a size andshape to receive a standard patch. The particular aperture cut bymachines of the type to which my invention pertains is of substantiallydouble circular segmental shape, which I shall term biconvex. The edgesof this aperture are inclined inwardly and down-. wardly and meet toform an angle at each end of the aperture.

One of the principal difiiculties which has been experienced with defectcutting machines of this type is their inability to make consistently aclean cut through a veneer sheet without stripping fibers of the Woodbeyond the aperture, especially at its end at which the cutters run out.

A principal object of my invention, thereforejs to construct a machinewhich will cut the margm of the aperture in the veneer sheet cleanly sothat it leaves the wood around the aperture intact. This object isaccomplished in two ways, namely, by improving the mounting for theholddown shoe which cooperates with the cutter head, and by controllingmovement of the cutter head relative to the veneer sheet, while the cutisbeing made, in a manner such that it will cut more efiectively nearcompletion of its stroke.

An advantage of my machine is that the structure employed foraccomplishing the above object need not becomplicated'. The holddownshoe is mounted so that it can be adjusted conveniently for the purposeof compensating .for wear occasioned by the use of the'machine, enablingthe effectiveness of the shoe to bemaintained over an extende'd'per'iod.

cantilever supportincluding spaced horizontal .b'eams l'l, preferabl'y of channel shape, which 1 The various advantageous .characteristics of mymachine will be pointed outingifeater detail in the following particulardescription of the embodiment of mymvenaon which I now prefer.

, Figure 1 is a front elevation view of the defect cutting machinajan'dFigure 2 is a side elevation view of the machine, with parts broken awayalong line2,2 of Figure 1. I

Figure 3 is a vertical sectional view through the cutter strokecontrolling cylinder of the machine,

Figure 4 a vertical sectional view through the work table and ho 1ddownshoe showing a portion of the cutter head in' elevation. Figure 5 is aplan view of an end portion of the holddown shoe, the balance of suchshoe and other parts beillg broken away.

, Figure 6 is a sectionalview through the holddown shoe and itsmountings taken on line 66 of Figure V d typical machine to which myinvention may be i'pplied, as illustratedin the drawings, in-

, clud'es a, table! on which a veneer sheet V is laid. Thistable hasanaperture I!) in it located immediately below, the vertically movablecutter Such" cutter. head is suspended from have correspondingendscarried by a post E2. The adjacentend's of these beams which aregen" e rally above the cutter head 2 are interconnected by abridgi'ngend plate i3.

The .cutterhead 2', is mounted directly on the axle 2'0journa'ledin'a'bearing 21 which is secured to the under side of a tilting bar 22.This bar rocks about a horizontal pivot 23 spaced a substantial distancefrom bearing 21, and the pivot is carried by" the lower end of alplate ii secured toa'nd depending froma'b'e'am I! of thecantilever ned a The"vertical disposition o fthe cutter head may thereforeberegulatedfbycontrolling the degree of tilt of bar 22 ab out its pivot. The cutterhead maye ariven rotatively b an electric motor 24 mounted on bar 22;atjfth'e side of pivot 23 opposite"the cutter head' 'bearing 2i.[Pulleys on the m tal; shaft essentials-cutte head sha ft 25c may beinterconnected byabelt 25pre fe'rably of the V type; This he neednothavany special tightiier arrangement beca se its length does net change asthe cutter head is raised and lowered, sincebotli'fthe incidentthecutter head shaft e ltirig bar 212 As the cutter :head is le w ere dthe motor will swing upward, and

western, in See SawfaShiOn,

The cutter head in side elevation may be of cruciform shape as shown inFigure 1. Each f its arms has secured to it a blade 26, preferably ofogival contour. When these cutters, moving in an arcuate path, passthrough a veneer sheet V they cut a biconvex aperture, the edges ofwhich are inclined inwardly and downwardly.

In order to hold the veneer sheet firmly during the cutting operation aholddown shoe 3, having in it a central opening to-receive the cutterhead, is arranged to be pressed down against the veneer sheet around thezone to be cut. This shoe must, of course, be raised and loweredgenerally in synchronism with the upward and downward movement of thecutter head in order to clamp and to release the veneer sheet at theproper time. The shoe is therefore supported by a hollow frame 3|]having a transparent door 3| to protect the operator from inadvertentlytouching the cutter head. This frame is guided for vertical movement byspaced guide rods 32 slidably received in bearings mounted on the frontface of the support plate l3. A crosshead 33 interconnects the upperends of the guide rods and has a lug 34 projecting rearwardly from itabove such plate.

Reciprocation of crosshead 33, and consequently frame 352 and its shoe3, is effected in synchronism with upward and downward movement of thecutter head by a rod 2'! having its upper end bearing slidably in a lugl3 projecting rearwardly from end plate I3. This bearing and lug 34 ofthe crosshead are disposed in alignment so that, when the end of bar 22carrying the cutter head swings upward, rod 21 will be pushed upward toengage its upper end with the lug, thus to raise the crosshead, guiderods 32 conected to it and frame 36.

As bar 22 is swung downward to lower the cutter head, rod 2'! also willbe drawn downward. The weight of frame 30, guide bars 32 and crosshead33 will tend to slide their assembly downward as the supporting force ofthe rod is removed, but in addition a substantial downward force will beexerted on the crosshead by a spring 35 having its upper end connectedto the crosshead and its lower end to a lug 28 projecting forward fromrod 21. After shoe 3 has engaged sheet V firmly the cutter head may bemoved downward farther, but the shoe cannot continue to move insynchronism. As rod 2? and its lug are drawn downward positively by bar22 after the shoe bears on the veneer sheet, spring 35 will stretch asit exerts an increasingly greater pull on crosshead 33 to augment thepressure of the shoe on the sheet to be cut.

Mechanism for tilting bar 22 is under the control of the operator, sothat the cutter head may be lowered when it is in registry with a defectin the veneer sheet. Such mechanism includes an upright rod 4 having itslower end pivoted to the end of bar 22 behind the cutter head. The

upper end of this bar is connected by a universal joint to one end of alever 4| tiltable about a pivot 42 which extends through the centralportion of such lever and is mounted in a base 43 supported from thesupport beams II.

The opposite end of lever 4| is swung by a compressed air or steamcylinder and piston 44 having their connecting rod 45 bearing upwardagainst the lever. The lever and piston are re turned into the positioncorresponding to the upper position of the cutter head by a tensionspring 46 interconnecting the lever and the base 43. To relieve rod 4from the necessity of returning the cutter head to its upper position, atension spring 4 41 is interconnected between a beam II and a lug 29integral with and projecting beyond the end of bar 22 which carries thecutter head bearing 2|.

The structure described thus far is not novel. My invention isparticularly concerned with the adjustment and control of such mechanismfor the purpose of producing a cleancut aperture in the veneer sheet,and in particular to prevent fibers of the wood at the outrunning end ofthe aperture being stripped out, instead of being severed cleanly. Inorder to accomplish this result with certainty I have found it desirableto locate the veneer sheet holddown shoe 3 so that the margin of itsaperture 36 lies closely adjacent to the upwardly moving cutter blades26 to serve as a chip breaker, and also to move the cutter head downwardsufficiently slowly with relation to its rotary speed to enable itscutters to effect a proper cutting action, rather than a tearing action.For the machine to be operated at an economical speed, however, thecutter head should not be depressed throughout its entire stroke at aspeed as slow as is desirable during the final portion of such stroke.

As the aperture is cut in the veneer sheet V, held down onto the table Iby the shoe 3, the sawdust particles are drawn upward through frame 30into a suitable suction conduit (not shown) connected to it. Theabrasive action of the wood particles as they are pressed by the cutters26 against the sides of the aperture 36 gradually enlarges this apertureso that its sides no longer lie closely adjacent to the cutters. Becauseof this wearing action on the sides of the aperture in the shoe itscentral portion 31 is customarily made removable, such as being formedof Babbitt metal. When the aperture becomes very badly worn, therefore,this central section may be melted out and a new portion cast in placehaving an aperture of the proper size.

It has been found that the sides of aperture 36 wear suflicientlyrapidly so that after a period of use even as short as one day theaperture, especially at the end from which the cutters emerge, namely atthe right in Figure 4, has become enlarged sufiiciently so that the chipcut by the cutter head is not broken cleanly, and iibers are strippedfrom the upper surface of the veneer sheet beyond the end of theintended aperture. Since the upper side of the veneer sheet is its faceside, the result is that the cutter head has cut out one defect, such asa knot or pitch pocket, only to form another defect, namely the strippeddepression. Prior to my invention the only remedy for this situation wasto replace the Babbitt metal center portion 31 of the shoe 3 almostevery day of operation, which obviously is impractical. Consequently thepractice was to patch by hand such defects as were caused by theaperture-cutting operation, and to repair the shoe 3 only when theaperture 36 had become so enlarged that a considerable proportion of theveneer apertures were defective.

I discovered that, because the margin of the veneer sheet aperture waswell supported from below at its left end by the table I, as seen inFigure 4, and the cutters 26 were moving downward, it was not necessaryfor the margin of the shoe aperture to lie very close to the cutters toenable them to produce a clean out. At the right end of the aperturebeing formed in the veneer sheet, however, the cutters press the sheetupward away from the table and against the holddown shoe 3. At thislocation it is necessary for the shoe -shown in'detail'in Figure 3. Itincludes. a-'hy-- "draul-ic damping cylinder receiving. a; piston-:50.

aperture ina'rgintotli osly'aloiig'side the fiath i fthefcutter'sfassho' o-lioldthe veneershee't 'firmlyjin opposition to theupwara force of the cutter head and to break the chip near mompletionofthe out.

For this purpose I provide a support -for the holddown shoe whichenables it dice-adjusted lengthwise "so that, despite any enlar g'ementof its aperture, its margin will lieclosely alongside the V path of theupwardly-moving cutters at the right in-Figure 4, although there 'inaybe a' considerable space'between 'the path of theidownwardly movingcutters and the a'perture' vvallfat the left end of the aperture withoutdetriment. In order to suppcrt tneence ror uh 'adjustment any er eanscstypesc stmoti'on connections "may be empieyedgpro 'that theyemaintainaccurately the "align-merit er -the s'hoe aperlture relative to thecutter head- 2.

-The particular 'sho'e supporting i'rnechanism shown includes'angle bars38 secured to opposite sides of frame Sir-so that-theirhorizontalxflan'ges 'lie'flush with the bottom "edge "of the frame.These flanges areslotted' along. lines i'perpen'dicularto" the" uprightflanges er 3 suchiiangles, :to receive' shoe clamping bolts'391'scre'wed into? tapped hoes' in the'respective' en'ds of the shoe 3.Such bolts may fit in-their grooves sufiiciently-fclosely to positionthe shoe accurately, but "preferably the horizontal flanges of angles 38have small downwardly projecting lugs 38" constituting keys whichfitsnugly ina keyw'ay 3' formed in-the upper sideof-the shoe at'each endtoposition it laterally.

Instead of requiring the shoe 3-tobe replaced} or the Babbitt metalinsert 31' to-be recast every day, my construction enables the'shoe tobe shifted toward the left in Figure 4 until the: sides of itsaperture36 at its ri'ght end 'justwclearthe path of cutters '26,- suchadjustment :being made several timeseach day, ifdesired. When theincreased clearance thus producedat the-leftend of the shoe aperturehasbecometoo'great, of course, after the shoe has been shifted endwiserepeatedly, the Babbitt metal insert' 31: may be 1 recast. I

While, as described, the disposition-ofshoe 3 to constitute an effectivechip breaker is'very important, the cutter should nevertheless be moveddownward slowlyn'ear the end of its-stroke to cutproperly, since thespeed-of cutter head rotation should not be excessive. It is not neces-"sary, however, for the cutter head-"to move" at such a slow speedthroughout its entire downward stroke. Because it is preferable not torely 'upon the operator to regulate the "speed -manually to produce thedesired result, I" have provided an'automatic control to effect downwardmovement of the cutter head-while cutting, at a progressively decreasingrate; and finally to bring it to a stop. The cutter head must not beallowed to move downward too -far, because it would form anape'rtureinthe veneer sheet V larger than the patch-which it is toreceive, and its bad'es'would cut into the convergent end surfaces ofapertu're"36 in shoe 3, making it too large to cooperatelproperly withthe cutters as a chip breaker.

The automatic stroke 'control mechanism' is The' piston rod- 5 I. isconnected "bya universal joint 52 toan' adju'sting-screw 53=threadedisin -lever 4|. "Such's'crew -may belocked: in any 'adwjusted'po'sition' :by the locknut which nmay 6 have an operating handle e55rproje'ctingsfromeit for ease of operation.

"A iby+pass massage 6 alongside zthe-ecylindeir 5 extends from alocation-rbelow arpluralityiof ibleed or metering orifices .69, 161,562and :6e,1:spaced man of the cylinder, upward :above a retum orifice :64,'1 which is 5 located in the-cylinder wall :above I the uppermostposition of the .upp'er surface of piston ifiil. The :piston'is;normally 2 urged upward by aspring tit-engaged betweentherlower "end ofcylinder 5 "and .aifiange 51aon:the:piston rod :i5l SpaQed"S1i:g'1Tb1y?b810W thGEOVEEI'ESUIffiGBKOf the piston. Above this flangeis an annularrclack valve '58 controlling the fiow of'liqnid through oneor more passages -59 extending axially through the piston outwardly ofpiston rod 5.5.1.. Thepiston rod projects downward within spring 56 farenough to prevent thespring bucklinggand. additionally to serve as-apositive "stop :for .thepiston and rod, which is "completely enclosedand. protected by the cylinder 5, and hence itsaccuracy cannot bealfected adversely by an accumu lationof dirt or sawdust between itscooperating parts. Nevertheless the terminal lower-:position of thecutter head is readily adjustable by-raising or lowering the "positionofleven-Alrelative to the piston rod by rotation of. screw 53.

As previously stated, the airor'steamgcylinder and piston 44 pressupward on the left encl' of lever M as seen in Figure 2 to depressthe-right end of that lever, and consequently to moverpush rod 4 and thecutter head downward. =By: reason of the interconnection shownin---Figures 2- and 3, piston rod 5! would be moved downwardsimultaneously. The pressure of piston-50 ion the liquid below it incylinder 5, caused by -,such downward movement, will immediately moveclack valve ring-58 upward to close pistong-passages 59, thus trappingthe liquidin the-lower end of cylinder 5 except as it may travel throughIcy-pass 6 to the upper-side of the piston. -Until the lower side of thevalve ring reaches the upper port 60 liquid will'be displaced through.-all of holes 60, 6!, 62 and 63, through passage-6 and into the upperend of cylinder 5 through port; 64.

Because of the substantial aggregate size ofthe several lower ports thetransfer of liquid through the by-pass from the lower end to the upperend of the cylinder will be reasonably fast at first, and consequentlythe downward travel of piston 50 and of cutter head 2 will be at acomparatively rapid rate, at least until the cutters have started to cutthe veneer sheet. Further downward movement of the piston will cause itto close first portBll, somewhat throttling the flow of fluid throughthe by-pass, then successively ports GI, 62 and 63. As each port isclosed the flow area for passage of liquid through the by-pass will bethrottled increasingly, and consequently the downward movement of thepiston and of the cutter head will be progressively retarded.

Such retardation of the cutter head movement is greater if the apertures88, 6 i, 62 and 63 are of progressively smaller size, as shownin Figure3. Although the cutter head moves comparatively rapidly while making thefirstportionof the cut, therefore, its rate of travel is varysubstantially, although smoothly, decreased as the =--cutting operationprogresses, depending upon-the spac- 'ing,.number and'size of, thecylinder.ports,.. so that the aperturein the veneer Sheetwill becutcleanly. I As soon asthe lower side of pistontfl has closed port fihtherem-ainder oftheliquid in -.the lower end of cylinder 5-willbe,tra,pped,-and #thecutter headwill be broughtto a.stop--by..en-

Yg'agement'of the lower end of piston rod with 'the bottom of thecylinder.

If the cylinder should leak so that there is not enough liquid in it tocome up to port 63 by the time the lower side of the piston hasdescended to cover this port, the rate of travel of the piston -will notbe retarded, but the lower end of piston rod 5| will engage the bottomof the cylinder to terminate downward movement of such rod and thecutter head positively, as a safety feature. iDuring normal operation,however, the rate of i'piston movement will decrease progressively, asdiscussed.

Preferably downward movement of the cutter head is timed automaticallyby regulating the :supply of air or steam to the space between theipiston and cylinder 44. Inflow of the pressure rfiuid may be controlledby a valve 1 operated by an electric solenoid and timer it ofconventional design. The operator need merely close the electric circuitto the valve actuating mechanism It, whereupon it will open the valve 5,hold it open for a predetermined length of time, and then close it.Venting of the cylinder will be controlled by the same mechanism toterminate the pressure exerted by connecting rod 45 on lever 4 so thatit and the cutter head may be returned by springs 46 and 41. As thedownward pressure on piston rod 5| is thus relieved spring 55 will movethe piston 50 and piston rod upward. The pressure of the upper side ofthe piston against the liquid above it in cylinder 5 will immediatelypress clack valve ring 58 downward to open the axial piston ports 59.The liquid may then return from the upper end of the cylinder to itslower end both through port 64, by-pass 6 and the lower cylinder ports,and through the piston ports. The liquid in the cylinder will thereforenot appreciably retard upward movement of the piston, and consequentlythe cutter head will be raised more rapidly than even its initialdownward travel.

To enable the various ports 60, 6 I, 62', 63 and 84 to be drilledinitially in the wall of cylinder 5 behind the by-pass chamber 6, and toafford .access to such ports for cleaning them periodical- .ly as may berequired, the outer wall of the bypass may have several holes in it eachclosed by :a plug 65.

Since downward movement of piston 50 is arrrested as soon as it hasclosed the lower bleed port 63, such disposition of the piston must becoordinated with the desired lowest position of the cutter head forcutting defects from veneer sheets of a given thickness. downwardmovement of the holddown sho 3 is -limited by engagement with the veneersheet, "whereas the cutter head 2 may continue to derscend after suchengagement until movement of piston 50, and consequently of rod 4 andlever ii, :is stopped. When defects must be cut from veneer sheetsthicker than that for which the machine is set, either shoe 3 must beshifted sl'ghtly to the right in Figure l, or downward movement of thecutter head must be terminated somewhat (earlier if its contact with thewalls of aperture 136 is to be prevented.

If it is desired that the upper profile of the :aperture in a veneersheet be the same size regardless of the thickness of the sheet, thelengthwise disposition of the shoe should not be altered for processingsheets of different thickness, but the stroke of cutter head 2 may belengthened or shortened by releasing locknut 54, adjusting screw 53appropriately, and again tightening the It will be evident that locknut. By such adjustment the same clearance between the upwardly movingcutters 26 and the right end of aperture 36, as seen in Figure 4, ispreserved. If, on the contrary, it is referred that the lower profile ofthe veneer sheet aperture be uniform regardless of the thickness of thesheet, the stroke of the cutter head should not be adjusted, but thelengthwise disposition of the holddown shoe would be altered to affordminimum clearance between the walls of its aperture and cutters 26 whenthe shoe 3 is resting on the upper surface of the veneer and the cutterhead is in its lowermost position.

I claim as my invention:

1. A defect cutting machine comprising a table to support a sheet to becut, a rotary cutter head having a plurality of blades rotatable aboutan axis generally parallel to said table, and supported above said tablefor movement from an upper position into a lower, defect-cuttingposition, a hold-down shoe, means interconnecting said shoe and tablefor relative movement between a released position in which said shoe isspaced a substantial distance above said table and a holding position inwhich said shoe and said table are close together for clampingtherebetween a sheet on said table to be cut, said shoe having anaperture therein adapted to receive said cutter head so its bladesnormally move close alongside the sides of such aperture when saidcutter head rotates in its defect-cutting position, said shoe being'shiftable relative to said supporting means parallel to said table andtransversely of said blade rotation axis, means automaticallycontrolling said cutter head to terminate downward movement thereof, andmeans operable to secure said hold-down shoe against movement relativeto said supporting means in any one of various positions adjustedtransversely of the rotative axis of said cutter head, to dispose suchshoe aperture with its sides close alongside the up wardly moving bladesof said cutter head when in its lowermost position during thedefect-cutting operation established by said automatic controllingmeans.

2. A defect cutting machine comprising a table to support a sheet to becut, a rotary cutter head having a plurality of blades rotatable aboutan axis generally parallel to said table, and supported above said tablefor movement from an upper position into a lower, defect-cuttingposition, a hold-down shoe, means supporting said shoe for movement froman upper released position spaced a substantial distance above saidtable into a lower holding position adjacent to said table forengagement with a sheet on said table to be cut, said shoe having anaperture therein adapted to receive said cutter head so its bladesnormally move close alongside the sides of such aperture when saidcutter head rotates in its defect-cutting position, means automaticallycontrolling said cutter head to terminate downward movement thereof,means guiding said shoe for linear movement relative to said supportingmeans parallel to said table and transversely of the cutter rotationaxis, clamping means operable to secure said hold-down shoe againstmovement relative to said supporting means in any one of variouspositions adjusted along a line generally parallel to said table andtransversely of the rotative axis of said cutter head, to dispose suchshoe aperture'with its sides close alongside the upwardly moving bladesof said cutter head when in its lowermost position during thedefect-cutting operation establishedby said automatic controlling means,and means restraining said shoe from movement relative to saidsupporting means transversely of such line of movement of said shoe.

3. A defect cutting machine comprising a table to support a sheet to becut, a rotary cutter head having a plurality of blades rotatable aboutan axis generally parallel to said table, and supported above said tablefor movement from an upper position into a lower, defect-cuttingposition, a hold-down shoe, means supporting said shoe for movement froman upper released position spaced a substantial distance above saidtable into a lower holding position adjacent to said table 'forengagement with a sheeton said table to be cut, said shoe having anaperture therein adapted to receive said cutter head so its bladesnormally move close alongside the sides of such aperture when saidcutter head rotates in its defect-cutting position, said shoe beingshiitable relative to said supporting means parallel to said table andtransversely of said blade rotation axis, means automaticallycontrolling said cutter head to retard downward movement thereofprogressively during the cutting operation, and means operable to securesaid holddown shoe against movement relative to said supporting means inany one of various positions adjusted transversely of the rotation axisof said cutter head to dispose such shoe aperture with its sides closealongside the upwardly moving blades of said cutter head when in itslowermost position during the defect-cutting operation.

4. The defect cutting machine defined in claim 3, in which the automaticcutter head controlling means, in addition to retarding, movement of thecutter head, incorporates means operable to terminate downward movementthereof in a predetermined lowermost position established by saidmovement terminating means. i

5. A defect cutting machine comprising a table to support a sheet to beout, a rotary cutter head having a plurality of blades rotatable aboutan axis generally parallel to said table, and supported above said tablefor movement from an upper position into a lower, defect-cuttingposition, a hold-down shoe, means supporting said shoe for movement froman upper released posi- 10 tion spaced a substantial distance above saidtable into a lower holding position adjacent to said table forengagement with a sheet on said table to be out, said shoe having anaperture therein adapted to receive said cutter head so its bladesnormally move close alongside the sides of such aperture when saidcutter head rotates in its defect-cutting position, said shoe beingshiftable relative to said supporting means parallel to said table andtransversely of said blade rotative axis, means automaticallycontrolling said cutter head to retard downward movement thereof to aprogressively greater degree as the cutting operation progresses, andfurther operable to terminate such downward movement thereof, adjustingmeans for said automatic cutter head controlling means operable todetermine the elevation of said cutter head in its defectcuttingposition, and securing means for said hold-down shoe operable to securesaid holddown shoe in any one of various positions adjusted transverselyof the rotative axis of said cutter head, said two adjusting meanscooperating to dispose said cutter head and said shoe at the completionof the cutting operation with the wall of the hold-down shoe apertureclose alongside the upwardly moving blades of said cutter headregardless of the spacing between the downwardly moving cutter headblades and the wall of such shoe aperture.

ELMER H. JACOBSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 743,37 Bresman Nov. 3, 1903972,479 Sondergard 1 Oct. 11, 1910 1,464,005 Kingsbury Aug. 7, 19231,548,773 Ziebarth Aug. 4, 1925 1,774,275 Johnson Aug. 26, 19301,942,414 Dumser Jan. 9, 1934 1,983,179 Maurer Dec. 4, 1934 2,071,519Gragg Feb. 23, 1937 2,142,022 Ernst Dec. 27, 1938

